Bi-objective design optimization for weldline reduction and short cycle time using variable injection velocity and variable packing pressure in plastic injection molding

Abstract

As weldline that is formed when two or more flow fronts meet has an influence on not only the appearance but also the strength of a plastic product, it is important to reduce it as much as possible. It has been reported that a high injection velocity is effective to the weldline reduction, but results in short shot. In addition to the weldline reduction, high productivity is always required in plastic injection molding. Thus, short cycle time is much preferable. For weldline reduction and short cycle time without short shot, this paper adopts variable injection velocity and variable packing pressure. Both profiles are unknown and it is difficult to determine them simultaneously. To determine both profiles, a bi-objective design optimization problem is constructed and the pareto-frontier between the weldline reduction and the cycle time is identified. Sequential approximate optimization using radial basis function network is used to identify the pareto-frontier with a small number of simulations. Based on the numerical result, the experiment is carried out to examine the validity of the proposed approach.

Keywords

• plastic injection molding
• engineering optimization
• multi-objective optimization
• computer aided engineering
• weldline